Mechanical locking system for panels and method of installing same

ABSTRACT

Floor panels are provided with a mechanical locking system including a flexible locking element in a locking groove which during a horizontal motion is displaced vertically.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/758,603, filed on Feb. 4, 2013, which is a continuation of U.S.application Ser. No. 13/253,283, filed on Oct. 5, 2011, now U.S. Pat.No. 8,387,327, which is a continuation of U.S. application Ser. No.12/962,341 filed on Dec. 7, 2010, now U.S. Pat. No. 8,079,196, which isa continuation of U.S. application Ser. No. 11/822,723, filed on Jul. 9,2007, now U.S. Pat. No. 7,866,110, which is a continuation of U.S.application Ser. No. 11/092,748, filed on Mar. 30, 2005, now U.S. Pat.No. 7,841,144. The entire contents of each of U.S. application Ser. No.13/758,603, U.S. application Ser. No. 13/253,283, U.S. application Ser.No. 12/962,341, U.S. application Ser. No. 11/822,723 and U.S.application Ser. No. 11/092,748 are hereby incorporated herein byreference.

TECHNICAL FIELD

The invention generally relates to the field of mechanical lockingsystems for floor panels and building panels.

FIELD OF APPLICATION OF THE INVENTION

The present invention is particularly suitable for use in floatingfloors, which are formed of floor panels which are joined mechanicallywith a locking system integrated with the floor panel, i.e., mounted atthe factory, are made up of one or more upper layers of veneer,decorative laminate or decorative plastic material, an intermediate coreof wood-fiber-based material or plastic material and preferably a lowerbalancing layer on the rear side of the core. The following descriptionof known techniques, problems of known systems and objects and featuresof the invention will therefore, as a non-restrictive example, be aimedabove all at this field of application and in particular laminateflooring formed as rectangular floor panels with long and short sidesintended to be mechanically joined on both long and short sides. Thelong and short sides are mainly used to simplify the description of theinvention. The panels could be square. It should be emphasized that theinvention can be used in any panel and it could be combined with alltypes of known locking systems, where the floor panels are intended tobe joined using a mechanical locking system connecting the panels in thehorizontal and vertical directions on at least two adjacent sides. Theinvention can thus also be applicable to, for instance, solid woodenfloors, parquet floors with a core of wood or wood-fibre-based materialand a surface of wood or wood veneer and the like, floors with a printedand preferably also varnished surface, floors with a surface layer ofplastic or cork, linoleum, rubber. Even floors with hard surfaces suchas stone, tile and similar are included and floorings with soft wearlayer, for instance needle felt glued to a board. The invention can alsobe used for joining building panels which preferably contain a boardmaterial for instance wall panels, ceilings, furniture components andsimilar.

BACKGROUND OF THE INVENTION

Laminate flooring usually comprises a core of a 6-12 mm fibre board, a0.2-0.8 mm thick upper decorative surface layer of laminate and a0.1-0.6 mm thick lower balancing layer of laminate, plastic, paper orlike material. A laminate surface comprises melamine impregnated paper.The most common core material is fibreboard with high density and goodstability usually called HDF—High Density Fibreboard. Sometimes alsoMDF—Medium Density Fibreboard—is used as core.

Traditional laminate floor panels of this type have been joined by meansof glued tongue-and-groove joints.

In addition to such traditional floors, floor panels have been developedwhich do not require the use of glue and instead are joined mechanicallyby means of so-called mechanical locking systems. These systems compriselocking systems, which lock the panels horizontally and vertically. Themechanical locking systems are usually formed by machining of the coreof the panel. Alternatively, parts of the locking system can be formedof a separate material, for instance aluminium or HDF, which isintegrated with the floor panel, i.e., joined with the floor panel inconnection with the manufacture thereof.

The main advantages of floating floors with mechanical locking systemsare that they are easy to install. They can also easily be taken upagain and used once more at a different location.

DEFINITION OF SOME TERMS

In the following text, the visible surface of the installed floor panelis called “front side”, while the opposite side of the floor panel,facing the sub floor, is called “rear side”. The edge between the frontand rear side is called “joint edge”. By “horizontal plane” is meant aplane, which extends parallel to the outer part of the surface layer.Immediately juxtaposed upper parts of two adjacent joint edges of twojoined floor panels together define a “vertical plane” perpendicular tothe horizontal plane.

By “locking systems” are meant co-acting connectors which connect thefloor panels vertically and/or horizontally. By “mechanical lockingsystem” is meant that joining can take place without glue. Mechanicallocking systems can in many cases also be joined by gluing. By“integrated with” means formed in one piece with the panel or a separatematerial factory connected to the panel.

KNOWN TECHNIQUES AND PROBLEMS THEREOF

For mechanical joining of long sides as well as short sides in thevertical and horizontal direction (direction D1, D2) several methodscould be used. One of the most used methods is the angle-snap method.The long sides are installed by angling. The panel is than displaced inlocked position along the long side. The short sides are locked byhorizontal snapping as shown in FIGS. 1 a-1 c. The vertical connectionis a tongue 10 and a groove 9 during the horizontal displacement, astrip 6 with a locking element 8 is bent and when the edges are incontact, the strip springs back and a locking element 8 enters a lockinggroove 14 and locks the panels horizontally. The vertical displacementof the locking element during the snapping action is caused by thebending of the strip. Such a snap connection is complicated since ahammer and a tapping block is frequently used to overcome the frictionbetween the long edges and to bend the strip during the snapping action.The friction on the long side could be reduced and the panels could bedisplaced without tools. The snapping resistance is howeverconsiderable, especially in locking systems made in one piece with thecore. Wood based materials are generally difficult to bend. Cracks inthe panel may occur during snapping and the locking element must berather small in the vertical direction in order to allow snapping.

It is known that a snap system could have a separate plastic strip 6′,integrated with the panel and with a resilient part as shown in FIGS. 1d-1 f. Such a locking system could be locked with less resistance thanthe traditional one-piece snap system. This locking system has howeverseveral disadvantages. The plastic strip is used to replace both thetongue and the strip with a locking element. The material cost istherefore high and the locking system is generally not compatible withthe locking system used in old panels. The groove 9 is difficult toproduce since it must have a locking element 8′. In fact 4 lockingelements, two flexible locking elements on the strip and two (8, 8′) inthe panel, must be used to lock in the horizontal direction. It isdifficult to fix the plastic strip over the whole length of the shortside. This means that corner portions will not have any tongue and thiscould cause problems in some applications.

SUMMARY AND OBJECTS

A first overall objective of the present invention is to provide alocking system, which could be locked by horizontal snapping and withless snapping resistance than the known systems. The costs and functionsshould be favourable compared to known technology. An aspect of theoverall objective is to improve the function and costs of those parts ofthe locking system that locks in the horizontal direction when panelsare pushed against each other.

More specifically an object is to provide a snap locking system whereone or several of the following advantages are obtained.

The floor panel should preferably be possible to displace and lock withsuch a low force that no tools will be needed.

The locking function should be reliable and the vertical and horizontallocking should be strong and prevent that two locked panels will movewhen humidity is changing or when people walk on a floor.

The locking system should be able to lock floor panels vertically withhigh precision so that the surfaces are essentially in the same plane.

The locking system should be designed in such a way that the materialand production costs could be low.

Another objective is to provide a snap locking system which could becompatible with traditional locking systems.

According to a first embodiment, a flooring system is provided,comprising a plurality of rectangular floor panels with long and shortedges, which are mechanically connectable to each other along one pairof adjacent edges. The floor panels are provided with tongue and grooveformed in one piece with the panels for mechanically locking togethersaid one pair of adjacent edges at right angles to the principal planeof the panels, thereby forming a vertical mechanical connection betweenthe panels. The panels are provided with a first locking element at onefirst edge formed in one piece with the panel and a locking groove at anopposite adjacent second edge, the locking groove being open towards arear side or a front side of the panel. Each panel is provided with asecond locking element, formed of a separate material and connected tothe locking groove. The first and second locking elements form amechanical connection locking the panels to each other horizontallyparallel to the principal plane and at right angles to the joint edges.The second locking element is flexible and resilient such that twopanels, can be mechanically joined by displacement of said two panelshorizontally towards each other, while at least a part of the secondlocking element at said second edges is resiliently displacedvertically, until said adjacent edges of the two panels are brought intoengagement with each other horizontally and the second locking elementat said second edge is displaced towards its initial position againstthe first locking element at the first edge.

Although it is an advantage to integrate the flexible locking elementwith the panel at the factory, the invention does not exclude anembodiment in which flexible locking elements are delivered as separatecomponents to be connected to the panel by the installer prior toinstallation.

The embodiment allows horizontal and vertical locking of all sides offloor panels with for instance an angling of the long sides, a simplehorizontal displacement along the long sides and snapping of the shortsides. In this preferred embodiment the flexible locking element is onthe short sides. It could be on the long side or on the long and shortsides.

The invention is especially suited for use in floor panels, which aredifficult to snap for example because they have a core, which is notflexible, or strong enough to form a strong snap locking system. Theinvention is also suitable for wide floor panels, for example with awidth larger than 20 cm, where the high snapping resistance is a majordisadvantage during installation, in panels where parts of the lockingsystem is made of a material with high friction, such as wood and inlocking systems which are produced with tight fit or without play oreven with pretension. Especially panels with such pretension where thelocking strip is bent in locked position and presses the panels togetherare very difficult to displace and snap. A locking system that reducesthe snapping resistance will decrease the installation time of suchpanels considerably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a-f illustrate known systems.

FIGS. 2 a-b Illustrate two embodiments of the invention.

FIGS. 3 a-c illustrate in several steps mechanical joining of floorpanels according to an embodiment of the invention.

FIGS. 4 a-d illustrate in several steps mechanical locking and unlockingof floor panels according to an embodiment of the invention.

FIGS. 5 a-c illustrate in several steps mechanical locking of floorpanels according to another embodiment of the invention.

FIGS. 6 a-e show embodiments of the invention.

FIGS. 7 a-h show different embodiments of a flexible locking element.

FIGS. 8 a-8 c show locking systems on long and short sides according toembodiments of the invention.

FIGS. 9 a-i show how known locking systems could be converted to alocking system according to an embodiment of the invention.

FIGS. 10 a-d show how the flexible locking element could be used as aflexible tongue enabling a vertical connection according to embodimentsof the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

To facilitate understanding, several locking systems in the figures areshown schematically. It should be emphasized that improved or differentfunctions can be achieved using combinations of the preferredembodiments. The inventor has tested all known and especially allcommercially used locking systems on the market in all types of floorpanels, especially laminate and wood floorings and the conclusion isthat at least all these known locking systems which have one or morelocking elements cooperating with locking grooves could be adjusted to asystem with one or more flexible locking elements according to theinvention. Most of them could easily be adjusted in such a way that theywill be compatible with the present systems. Several flexible lockingelements could be located in both adjacent edges, one over the other orside-by-side. The flexible locking element could be on long and/or shortsides and one side with a flexible locking element could be combinedwith another side which could have all known locking systems, preferablylocking systems which could be locked by angling or a vertical movement.The invention does not exclude floor panels with flexible lockingelements on for example a long and a short side. Such panels could beinstalled by the known snap-snap installation methods. A preferredembodiment is a floorboard with a surface layer of laminate, a core ofHDF and a locking system with a flexible locking element on the shortside allowing easy snapping combined with a one piece mechanical lockingsystem on long side which could be locked by angling. The long sidelocking system could have a small play of some 0.01 mm between at leastsome surfaces which are active in the vertical or horizontal lockingsuch as tongue/groove and or locking element/locking groove. This smallplay facilitates displacement. Such a floorboard will be very easy toinstall with angling and snapping. Angles, dimensions, rounded partsetc. are only examples and could be adjusted within the principles ofthe invention.

A first preferred embodiment of a floor panel 1, 1′ provided with amechanical locking system according to the invention is now describedwith reference to FIGS. 2 a-2 b.

FIG. 2 a illustrates schematically a cross-section of a joint preferablybetween a short side joint edge 5 a of a panel 1 and an opposite shortside joint edge 5 b of a second panel 1′.

The front sides of the panels may include one or more upper layers of adecorative plastic material 61, and are essentially positioned in acommon horizontal plane HP, and the upper parts of the joint edges 5 a,5 b abut against each other in a vertical plane VP. The mechanicallocking system provides locking of the panels relative to each other inthe vertical direction D1 as well as the horizontal direction D2.

To provide joining of the two joint edges in the D1 and D2 directions,the edges of the floor panel have a locking strip 6 with a first lockingelement 8, and a groove 9 made in one piece with the panel in one jointedge 5 a and a tongue 10 made in one piece with the panel at an oppositeedge 5 b. The tongue 10 and the groove 9 and provide the verticallocking D1.

The mechanical locking system comprises a separate flexible secondlocking element 15 connected into a locking groove 14 formed in theopposite edge 5 b of the panel. Parts of the flexible locking elementcould bend in the length direction and could be displaced in the lockinggroove. The flexible locking element 15 has a groove portion P1 that islocated in the locking groove 14 and a projecting portion P2 projectingoutside the locking groove 14. The projecting portion P2 of the secondflexible locking element 15, made of a separate material, in one of thejoint edges cooperates with a first locking element 8 made in one piecewith the panel and formed in the other joint edge.

In this embodiment, the panel 1 could for example have a body or core 60of wood-fibre-based material such as HDF, plywood or solid wood, orplastic material. The panels 1, 1′ could also be made of stone, metal orceramic materials. These materials are not flexible. The tongue 10and/or the strip 6 with the locking element 8 could also be made of aseparate material connected to the panel.

The flexible locking element 15 has a protruding part P2 with a roundedouter part 31 and a sliding surface 32 which in this embodiment isformed like a bevel.

The first locking element 8 has a first locking surface 20 whichcooperates with a second locking surface 22 of the second flexiblelocking element 15 and locks the joint edges 5 a, 5 b in a horizontaldirection D2. In this embodiment, the locking surfaces 20, 22 areslightly angled (A) against the vertical plane VP. The second lockingelement 15 will therefore lock as a wedge and tolerances could beeliminated with vertical pre-tension caused by the vertical flexibilityof the second flexible locking element.

FIG. 2 b shows another embodiment. The inner part P1 of the flexiblelocking element 15 is fixed in the locking groove 14 and the protrudingpart P2 could flex vertically towards the locking groove 14 and theinner part P1 and back again towards the first locking element. In thisembodiment the bending of the protruding part P2 takes place around acenter point CP. The locking surfaces 20, 22 are formed such that theymeet each other when the protruding part P2 snaps back towards itsinitial position.

FIGS. 3 a-3 c show how the flexible locking element 15 is displaced inthe locking groove 14. The flexible locking element 15 is displacedvertically when the displacement surface 32 presses against the beveledpart of the first locking element 8 as shown in FIG. 3 a. When the topedges of the panels 1, 1′ are in contact or in the intended lockedposition, the flexible locking element 14 springs back and locks to thefirst locking element 8 as shown in FIG. 3 c.

FIGS. 4 a-4 c show that a locking system with a flexible locking element15 could also be locked and unlocked with angling. FIG. 4 d shows that alocking system with a flexible locking element could be unlocked with aneedle shaped tool 16, which is inserted along the joint edge to pushback the flexible locking element 14 and to unlock the locking system.Such an unlocking could be used to unlock panels which are installed ina herringbone pattern long side to short side with angling of shortsides and snapping of short sides to long side.

FIGS. 5 a-5 c show locking according to the embodiment in FIG. 2 b. Itis an advantage if the tip 11 of the tongue 10 is partly in the groove 9when the sliding surface 32 is in contact with the locking element 8.This facilitates snapping and installation of the panels.

FIGS. 6 a-6 e show different embodiments of the invention. FIG. 6 ashows a system with two tongues 10,10′ and with a locking groove 14 opentowards the front side. FIG. 6 b shows a system with the locking groovepartly in the part of the tongue 10 which is outside the vertical planeVP. FIGS. 6 c and 6 d are similar to 6 a but these systems have only onetongue. FIG. 6 e shows an embodiment according to FIG. 2 b but with thelocking groove open towards the front side. In this embodiment the floorpanel is a parquet floor with a surface layer of wood and a lamellacore. The flexible locking element 15 has a protrusion 36 to increasethe friction between the flexible locking element 15 and the lockinggroove 14.

The flexible locking element 15 should preferably be connected to thelocking groove with high precision, especially when parts of theflexible locking element 15 are displaced in the locking groove 14during locking. Depending on the compressibility and friction betweenthe flexible locking element and the locking groove, the flexiblelocking element as whole or different parts could be connected with asmall play, for example 0.01-0.10 mm, a precise fit or a pretension. Waxor other friction reducing materials or chemicals could be applied inthe locking groove and/or between the locking elements.

Even with a play, a precise fit between the upper joint edges could beaccomplished. The protruding part P2 could be formed to press againstthe locking surface 20 of the locking element 8. For example theprotruding part P2 could be formed with a small angle to the verticalplane VP. The protruding part P2 of the flexible tongue will tilt andpress the edges together. The flexible locking element 15 could beformed to cause a permanent pressure force vertically in the lockedposition. This means that the flexible locking element 15 will onlypartly spring back to the initial position. The flexible locking elementcould optionally be designed with such dimensions that after locking itwill move slightly towards its initial position. Gradually a perfectconnection will be accomplished.

FIGS. 7 a-7 h shows different embodiments of the flexible lockingelement 15. In FIG. 7 a the flexible locking element 15 is moulded andhas on one of the edge sections ES a friction connection 36 which couldbe shaped for instance as a local small protrusion. This frictionconnection keeps the flexible locking element in the locking groove 14during installation, or during production, packaging and transport, ifthe flexible locking element is integrated with the floor panel at thefactory. In FIG. 7 b the flexible locking element 15 is an extrudedplastic section.

FIG. 7 c shows a blank 50 consisting of several flexible lockingelements 15 connected to each other. In this embodiment the flexiblelocking element 15 is made with moulding, preferably injection moulding.

Any type of polymer materials could be used to produce the flexiblelocking elements such as PA (nylon), POM, PC, PP, PET or PE or similarmaterials having the properties described above in the differentembodiments. These plastic materials could be reinforced with forinstance glass fibre. A preferred material is glass fiber reinforced PA.

FIGS. 7 d and 7 e show a flexible locking element 15 with a length L,and a middle section MS and edge sections ES along the length L. Thisflexible locking element could bend in the length direction and theprotruding part P2 could be displaced vertically in the locking grooveif a force F is applied to the protruding part P2. FIG. 7 e shows thatthe displacement the middle section MS is larger than the displacementof the edge sections ES. FIG. 7 d shows that the size of the protrudingpart P2 and/or the groove portion P1 varies along the length L of theflexible locking element 15. FIG. 7 f shows a double tongue 15. FIG. 7 gshows an extruded section with a resilient punched inner part P1. FIG. 7h shows a flexible tongue 15 with protruding parts P2 at the edgesections ES.

With these production methods and basic principles a wide variety ofcomplex two and three-dimensional shapes could be produced at low cost.Of course the flexible locking element 15 could be made from metal,preferably aluminium, but wood based sheet material such as HDF andcompact laminate could also be used to form flexible locking elementswith machining and punching and in combination with for example flexiblerubber materials or similar.

FIGS. 8 a-8 c show how the flexible locking element 15 is connected to agroove 14 at a short side 5 a of a floor panel. FIG. 8 a shows anembodiment with a flexible tongue as shown in FIG. 7 b and FIG. 8 bshows an embodiment according to FIG. 7 a. FIG. 8 c shows a floor panelwith a flexible locking element on the short sides 5 a, 5 b and anangling system C, D on the long sides 4 a, 4 b. Of course the long sidescan also have one or several flexible locking elements. The flexiblelocking element 15 has in this embodiment a length L that is smallerthan the width FL of the floor panel. As a non-restricting example itcould be mentioned that sufficient locking strength could be achievedwith a flexible locking element with a length L which is smaller than0.8 times the floor width FW. Even a length L of 0.5 times FW could besufficient. Such a flexible locking element could have a weight of about1 gram and the material cost could be considerably lower than for otherknown technologies where separate materials are used. It is also veryeasy to connect to the locking element since it is not very importantthat the flexible locking element is connected at a precise distancefrom the corner portions 23. A further advantage is that the tongue 10extends along essentially the whole short side as in traditional floorpanels. This gives a strong vertical connection especially at the cornerportions 23. Of course the flexible locking element could coveressentially the whole width FW.

The flexible locking element could be connected to the locking groove inseveral ways. A preferable method is that the flexible locking elementis mechanically fixed. Of course glue or mechanical devices can also beused. To simplify the understanding the panel is located with its rearside up and the flexible locking element is on the short side. The panelcould also be turned with the front side up. The flexible lockingelement is separated from blanks 50, if it is moulded, or from rolls ifis extruded. It is then pressed or rolled into the locking groove when ashort side of the panel is displaced under a fixing unit and the lockingelement is connected with friction. A lot of alternatives are possiblewithin the main principles that the flexible locking element isseparated and fixed with a friction force.

FIGS. 9 a to 9 i are examples which show that known locking systems,especially traditional snap systems with a bendable strip (9 a-9 c or 9g-9 i) or lip 6 9 d-9 f) could be adjusted to a snap system with aflexible locking element 14 according to the invention. Generally only asimple adjustment of the locking groove is necessary. It could be madein the same machine and with the same number of cutting tools.

FIGS. 10 a-10 d show that the principles used in a locking system with aflexible locking element could also be used to replace the tongue 10with a flexible tongue 30 in order to provide a locking system, whichcould be locked by vertical folding. One panel 1′ could be moved alongthe vertical plane VP vertically towards another panel 1. The flexibletongue 30 is in this case displaced horizontally according to the sameprinciples as described for the flexible locking element and allembodiments of the flexible locking element could be used. Of course theflexible locking element could be combined with a flexible tongue. Sucha locking system could be locked with angling, snapping and verticalfolding. FIG. 10 d shows that it is an advantage if the flexible tongue30 on a short side is positioned between the upper and lower parts ofthe tongue 10′ and groove 9′ on the long sides. This gives a strongerlocking at the corner portions. FIG. 10 a shows that the sideward opengroove may be positioned in a joint plane (at the vertical plane VP)between the pair of adjacent edges of panels 1, 1′. FIGS. 10 b through10 c show that the locking element protrudes vertically from the lockingstrip and that bottommost part of the sideward open groove may bepositioned above an uppermost part of the locking strip.

Within the invention a lot of alternatives are possible to accomplishsnapping with a flexible locking element.

All features of the embodiment described above could be combined witheach other or used separately. They could be used on long and/or shortsides. The method to produce a separate locking element, which isinserted into a groove, could of course be used to improve frictionproperties and strength even if the locking element is not flexible ordisplaceable in the vertical direction. The methods and principles couldalso be used together with a flexible tongue that could be bent inhorizontal direction during locking. The flexible locking element couldalso be combined with a strip 6 or lip which is partly bent duringsnapping. The degree of such a bending could be considerable smallerthan in present known systems.

The system could be used to connect tile shaped panels installed on awall. The tiles could be connected to each other and to a locking memberfixed to the wall.

It will be apparent to those skilled in the art that variousmodifications and variations of the present invention can be madewithout departing from the spirit and scope of the invention. Thus, itis intended that the present invention include the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The invention claimed is:
 1. A set of floor panels which aremechanically connectable to each other along one pair of adjacent edges,each of said floor panels comprising: one or more upper layers of adecorative plastic material, and an intermediate core of a plasticmaterial; a flexible tongue on a first edge of the panel; a tonguegroove on a second edge of the panel for receiving the flexible tongueof an adjacent panel for mechanically locking together said adjacentedges at right angles to a principal plane of the panels thereby forminga vertical mechanical connection between the panels, wherein the tonguegroove is formed in a core of the panel; and a locking element formed inone piece with the panel at the first or the second edge and a lockinggroove at the other of the first or the second edge, the locking groovebeing open towards a rear side of the panel that faces a subfloor;wherein the locking element and the locking groove form a horizontalmechanical connection for locking the panels to each other horizontallyparallel to the principal plane and at right angles to the joined firstand second edges, wherein the flexible tongue is resilient and formed ofa separate material than the core, and cooperates with the tonguegroove, wherein two of the panels can be mechanically joined together bydisplacement of said two panels vertically towards each other while atleast a part of the flexible tongue is resiliently displacedhorizontally until said adjacent edges of the two panels are broughtinto engagement with each other vertically and the tongue is thendisplaced towards its initial position against the tongue groove,wherein the flexible tongue has an inner part mounted in a sideward opengroove, in the first or the second edge, and a protruding part, whereinthe inner part is fixed in the sideward open groove, and wherein thepart of the tongue which is resiliently displaced is the protruding partby bending around a center point located at an upper part of theprotruding part during locking of the panels together.
 2. The set offloor panels as claimed in claim 1, wherein the uppermost part of theflexible tongue is within the sideward open groove.
 3. The set of floorpanels as claimed in claim 1, wherein the locking element is formed inone piece with the panel at the first edge and the locking groove is atthe second edge.
 4. The set of floor panels as claimed in claim 3,wherein the locking element protrudes vertically from a locking stripand wherein a bottom most part of the sideward open groove is positionedabove an uppermost part of the locking strip.
 5. The set of floor panelsas claimed in claim 2, wherein the locking element is formed in onepiece with the panel at the first edge and the locking groove is at thesecond edge.
 6. The set of floor panels as claimed in claim 4, whereinthe sideward open groove is positioned in a joint plane between saidpair of adjacent edges.
 7. The set of floor panels as claimed in claim6, wherein the sideward open groove is positioned close to an upperdecorative surface of the panel.
 8. The set of floor panels as claimedin claim 1, wherein the protruding part comprises a first lockingsurface at a lower point of the protruding part and the tongue groove inthe second edge comprises a second locking surface at its lower outerpart and the first and the second locking surfaces are configured tocooperate to obtain the vertical locking.
 9. The set of floor panels asclaimed in claim 1, wherein the protruding part has a sliding surfacewhich extends downwards.
 10. The set of floor panels as claimed in claim1, wherein the flexible tongue is made of polymer material.
 11. The setof floor panels as claimed in claim 1, wherein the flexible tongue is ofa molded or extruded polymer material reinforced with glass fiber. 12.The set of floor panels as claimed in claim 11, wherein the polymermaterial is a thermoplastic material.
 13. The set of floor panels asclaimed in claim 10, wherein the polymer material is a thermoplasticmaterial.
 14. The set of floor panels as claimed in claim 1, wherein theinner part of the flexible tongue is provided with a protrusion tofacilitate a mechanical connection between the flexible tongue and thesideward open groove.
 15. The set of floor panels as claimed in claim 1,wherein each of said floor panels comprises a lower balancing layer onthe rear side of the core.
 16. The set of floor panels as claimed inclaim 1, wherein each of said floor panels comprises a second tongue ona third edge of the panel and a second tongue groove on a fourth edge ofthe panel for receiving the second tongue of an adjacent panel formechanically locking together said third and fourth edges at rightangles to a principal plane of the panels thereby forming a verticalmechanical connection between the panels, wherein the flexible tongue ispositioned between an upper and a lower part of the second tonguegroove.
 17. The set of floor panels as claimed in claim 1, wherein theuppermost part of the protruding part is within the sideward open groovebefore displacement of said two panels vertically towards each other.